None of mine ever ate plant roots but the only plants I had with exposed roots was Java Fern and that is pretty tough. If you have some algae on the glass, and offer them some fruit/ veges (pumpkin, zucchini, etc) each day, then that and the wood should be sufficient.
Good plants to try include Ambulia, Elodia, Hygrophilla polysperma, Swordplants & Narrow Vallis.
Have a light on the tank for about 12 hours a day. If you don't get much algae you can increase it a few hours. You can have the lights on for up to 16hours per day but the fish and plants need an 8 hour rest period.
You can also try adding some liquid plant food like Sera Florena and that will help.